The lack of stable p-type van der Waals(vdW)semiconductors with high hole mobility severely impedes the step of low-dimensional materials entering the industrial circle.Although p-type black phosphorus(bP)and telluriu...The lack of stable p-type van der Waals(vdW)semiconductors with high hole mobility severely impedes the step of low-dimensional materials entering the industrial circle.Although p-type black phosphorus(bP)and tellurium(Te)have shown promising hole mobilities,the instability under ambient conditions of bP and relatively low hole mobility of Te remain as daunting issues.Here we report the growth of high-quality Te nanobelts on atomically flat hexagonal boron nitride(h-BN)for high-performance p-type field-effect transistors(FETs).Importantly,the Te-based FET exhibits an ultrahigh hole mobility up to 1370 cm^(2) V^(−1) s^(−1) at room temperature,that may lay the foundation for the future high-performance p-type 2D FET and metal-oxide-semiconductor(p-MOS)inverter.The vdW h-BN dielectric substrate not only provides an ultra-flat surface without dangling bonds for growth of high-quality Te nanobelts,but also reduces the scattering centers at the interface between the channel material and the dielectric layer,thus resulting in the ultrahigh hole mobility.展开更多
In this work,the GaN p-MISFET with LPCVD-SiN_(x) is studied as a gate dielectric to improve device performance.By changing the Si/N stoichiometry of SiN_(x),it is found that the channel hole mobility can be effectivel...In this work,the GaN p-MISFET with LPCVD-SiN_(x) is studied as a gate dielectric to improve device performance.By changing the Si/N stoichiometry of SiN_(x),it is found that the channel hole mobility can be effectively enhanced with Si-rich SiN_(x) gate dielectric,which leads to a respectably improved drive current of GaN p-FET.The record high channel mobility of 19.4 cm2/(V∙s)was achieved in the device featuring an Enhancement-mode channel.Benefiting from the significantly improved channel mobility,the fabricated E-mode GaN p-MISFET is capable of delivering a decent-high current of 1.6 mA/mm,while simultaneously featuring a negative threshold-voltage(VTH)of–2.3 V(defining at a stringent criteria of 10μA/mm).The device also exhibits a well pinch-off at 0 V with low leakage current of 1 nA/mm.This suggests that a decent E-mode operation of the fabricated p-FET is obtained.In addition,the VTH shows excellent stability,while the threshold-voltage hysteresisΔVTH is as small as 0.1 V for a gate voltage swing up to–10 V,which is among the best results reported in the literature.The results indicate that optimizing the Si/N stoichiometry of LPCVD-SiN_(x) is a promising approach to improve the device performance of GaN p-MISFET.展开更多
(Ga,Fe)Sb is a promising magnetic semiconductor(MS)for spintronic applications because its Curie temperature(T_(C))is above 300 K when the Fe concentration is higher than 20%.However,the anisotropy constant Ku of(Ga,F...(Ga,Fe)Sb is a promising magnetic semiconductor(MS)for spintronic applications because its Curie temperature(T_(C))is above 300 K when the Fe concentration is higher than 20%.However,the anisotropy constant Ku of(Ga,Fe)Sb is below 7.6×10^(3)erg/cm^(3)when Fe concentration is lower than 30%,which is one order of magnitude lower than that of(Ga,Mn)As.To address this issue,we grew Ga_(1-x-y)Fe_(x)Ni_(y)Sb films with almost the same x(≈24%)and different y to characterize their magnetic and electrical transport properties.We found that the magnetic anisotropy of Ga_(0.76-y)Fe_(0.24)Ni_(y)Sb can be enhanced by increasing y,in which Ku is negligible at y=1.7%but increases to 3.8×10^(5)erg/cm^(3)at y=6.1%(T_(C)=354 K).In addition,the hole mobility(μ)of Ga_(1-x-y)Fe_(x)Ni_(y)Sb reaches 31.3 cm^(2)/(V∙s)at x=23.7%,y=1.7%(T_(C)=319 K),which is much higher than the mobility of Ga_(1-x)Fe_(x)Sb at x=25.2%(μ=6.2 cm^(2)/(V∙s)).Our results provide useful information for enhancing the magnetic anisotropy and hole mobility of(Ga,Fe)Sb by using Ni co-doping.展开更多
The structural property of GaSb epilayers grown on semi-insulator GaAs （001） substrate by metalorganic chemical vapor deposition （MOCVD） using Triethylgallium （TEGa） and trimethylantimony （TMSb）, was investiga...The structural property of GaSb epilayers grown on semi-insulator GaAs （001） substrate by metalorganic chemical vapor deposition （MOCVD） using Triethylgallium （TEGa） and trimethylantimony （TMSb）, was investigated by variation of the Sb：Ga （V/Ill） ratio. An optimum V/Ill ratio of 1.4 was determined in our growth conditions. Using transmission electron microscopy （TEM）, we found that there was an interracial misfit dislocations （IMF） growth mode in our experiment, in which the large misfit strain between epilayer and substrate is relaxed by periodic 90 deg. IMF array at the hetero-epitaxial interface. The rms roughness of a 300 nm-thick GaSb layer is only 2.7 nm in a 10μm×10μm scan from atomic force microscopy （AFM） result. The best hole density and mobility of 300 nm GaSb epilayer are 5.27xi06 cm-3（1.20×106） and 553 cm2-V-l.s-1 （2340） at RT （77 K） from Hall measurement, respectively. These results indicate that the IMF growth mode can be used in MOCVD epitaxial technology similar to molecular beam epitaxy （MBE） technology to produce the thinner GaSb layer with low density of dislocations and other defects on GaAs substrate for the application of devices.展开更多
Molybdenum ditelluride （MoTe2） has been demonstrated great potential in electronic and optoelectronic applications. However, the reported effective hole mobility remains far below its theoretical value. Herein, taki...Molybdenum ditelluride （MoTe2） has been demonstrated great potential in electronic and optoelectronic applications. However, the reported effective hole mobility remains far below its theoretical value. Herein, taking advantage of high-κ screening effect, we have fabricated back-gated MoTe2 transistors on an Al2O3 high-κ dielectric and systematically investigated the electronic and optoelectronic proper- ties. A high current on/off ratio exceeding 106 is achieved in the Al2O3-based MoTe2 transistors, and the hole mobility is demonstrated to be 150 cm2 V^-1 s^-1, compared to 0.2-20 cm^2 V^-1 s^-1 ever obtained from back-gated MoTe2 transistors in the literatures. Moreover, a considerable hole concentration of 1.2 × 10^13 cm 2 is attained in our Al2O3-based MoTe2 transistors owing to the strong gate control capa- bility, leading to a high on-state hole current of 6.1 μA μm^-1. After optimization, our Al2O3-based MoTe2 phototransistor exhibits outstanding photodetective performance, with a high responsivity of 543 AW^-1 and a high photogain of 1,662 at 405 nm light illumination, which are boosted around 419 times compared to the referential SiO2-based control devices. The mechanisms of photoconductivity in the Al2O3-based MoTe2 phototransistors have been analyzed in detail, and the photogating effect is considered to play an important role. This work may provide useful insight to improve carrier mobility in two-dimensional layered semiconductors and open opportunities to facilitate the development of high-performance photodetectors in the future.展开更多
In this work,silicon-germanium(SiGe)thin films are epitaxially grown on Ge substrates by ultra-high vacuum chemical vapor deposition and then doped with Mn element by ion-implantation and subsequent rapid thermal anne...In this work,silicon-germanium(SiGe)thin films are epitaxially grown on Ge substrates by ultra-high vacuum chemical vapor deposition and then doped with Mn element by ion-implantation and subsequent rapid thermal annealing(RTA).The characterizations show that the epitaxial SiGe thin films are single-crystalline with uniform tensile strain and then become polycrystalline after the ion implantation and following RTA.The magnetization measurements indicate that the annealed thin films exhibit Mn concentration-dependent ferromagnetism up to 309 K and the X-ray magnetic circular dichroism characterizations reveal the spin and orbital magnetic moments from the substitutional Mn element.To minimize the influence of anomalous Hall effect,magneto-transport measurements at a high magnetic field up to 31 T at 300 K are performed to obtain the hole mobility,which reaches a record-high value of~1230 cm^(2)V^(-1)s^(-1),owing to the crystalline quality and tensile strain-induced energy band modulation of the samples.The first demonstration of Mn-doped SiGe thin films with roomtemperature ferromagnetism and high carrier mobility may pave the way for practical semiconductor spintronic applications.展开更多
Utilizing a six-band k.p valence band calculations that considered a strained perturbation Hamiltonian, uniaxial stress-induced valence band structure parameters for Ge such as band edge energy shift, split, and effec...Utilizing a six-band k.p valence band calculations that considered a strained perturbation Hamiltonian, uniaxial stress-induced valence band structure parameters for Ge such as band edge energy shift, split, and effective mass were quantitatively evaluated. Based on these valence band parameters, the dependence of hole mobility on uniaxial stress(direction, type, and magnitude) and hole transport direction was theoretical studied. The results show that the hole mobility had a strong dependence on the transport direction and uniaxial stress. The hole mobility enhancement can be found for all transport directions and uniaxial stess configurations, and the hole transport along the [110] direction under the uniaxial [110] compressive stress had the highest mobility compared to other transport directions and stress configurations.展开更多
A physical model of hole mobility for germanium-on-insulator p MOSFETs is built by analyzing all kinds of scattering mechanisms, and a good agreement of the simulated results with the experimental data is achieved, co...A physical model of hole mobility for germanium-on-insulator p MOSFETs is built by analyzing all kinds of scattering mechanisms, and a good agreement of the simulated results with the experimental data is achieved, confirming the validity of this model. The scattering mechanisms involved in this model include acoustic phonon scattering, ionized impurity scattering, surface roughness scattering, coulomb scattering and the scattering caused by Ge film thickness fluctuation. The simulated results show that the coulomb scattering from the interface charges is responsible for the hole mobility degradation in the low-field regime and the surface roughness scattering limits the hole mobility in the high-field regime. In addition, the effects of some factors, e.g. temperature, doping concentration of the channel and the thickness of Ge film, on degradation of the mobility are also discussed using the model, thus obtaining a reasonable range of the relevant parameters.展开更多
Hole mobility changes under uniaxial and combinational stress in different directions are characterized and analyzed by applying additive mechanical uniaxial stress to bulk Si and SiGe-virtual-substrate-induced strain...Hole mobility changes under uniaxial and combinational stress in different directions are characterized and analyzed by applying additive mechanical uniaxial stress to bulk Si and SiGe-virtual-substrate-induced strained- Si（s-Si）p-MOSFETs（metal-oxide-semiconductor field-effect transistors）along 110 and 100 channel directions. In bulk Si,a mobility enhancement peak is found under uniaxial compressive strain in the low vertical field.The combination of 100 direction uniaxial tensile strain and substrate-induced biaxial tensile strain provides a higher mobility relative to the 110 direction,opposite to the situation in bulk Si.But the combinational strain experiences a gain loss at high field,which means that uniaxial compressive strain may still be a better choice.The mobility enhancement of SiGe-induced strained p-MOSFETs along the 110 direction under additive uniaxial tension is explained by the competition between biaxial and shear stress.展开更多
The hole mobility of strained silicon along the <110> orientation on (001) Si1?xGex is obtained by solving collision term in the Boltzmann transport equation. The analytical model is proposed that considers the ...The hole mobility of strained silicon along the <110> orientation on (001) Si1?xGex is obtained by solving collision term in the Boltzmann transport equation. The analytical model is proposed that considers the effect of strain-induced splitting at valence band valleys in silicon, doping dependence and three scattering mechanisms, i.e., ionized impurity scattering, acoustic phonon scattering and non-polar optical phonon scattering. The hole occupancy at top band indicates a non-monotonic variation under biaxial tensile strain at low temperature (77 K). What's more, a non-monotonic variation of hole mobility at room temperature (300 K) is presented. Compared with the room temperature hole mobility, the low temperature hole mobility is affected greatly by ionized impurity scattering at lower impurity concentration. At the same time, the room temperature hole mobility is lower than that of electron with the same germanium content and doping concentration. If the parameters are correctly chosen, the model can also be used to calculate the hole mobility of other crystal faces with arbitrary orientation. So, it lays a useful foundation for strained silicon devices and circuits.展开更多
First-principles approaches have recently been developed to replace the phenomenological modeling approaches with adjustable parameters for calculating carrier mobilities in semiconductors.However,in addition to the h...First-principles approaches have recently been developed to replace the phenomenological modeling approaches with adjustable parameters for calculating carrier mobilities in semiconductors.However,in addition to the high computational cost,it is still a challenge to obtain accurate mobility for carriers with a complex band structure,e.g.,hole mobility in common semiconductors.Here,we present a computationally efficient approach using isotropic and parabolic bands to approximate the anisotropy valence bands for evaluating group velocities in the first-principles calculations.This treatment greatly reduces the computational cost in two ways:relieves the requirement of an extremely denseκmesh to obtain a smooth change in group velocity,and reduces the 5-dimensional integral to 3-dimensional integral.Taking Si and SiC as two examples,we find that this simplified approach reproduces the full first-principles calculation for mobility.If we use experimental effective masses to evaluate the group velocity,we can obtain hole mobility in excellent agreement with experimental data over a wide temperature range.These findings shed light on how to improve the first-principles calculations towards predictive carrier mobility in high accuracy.展开更多
Although lots of efforts have been devoted on new less hygroscopic dopants to address problems in hole transport materials(HTM),the long-time post-oxidation and the volatilization of 4-tert-butylpyridine(tBP)are still...Although lots of efforts have been devoted on new less hygroscopic dopants to address problems in hole transport materials(HTM),the long-time post-oxidation and the volatilization of 4-tert-butylpyridine(tBP)are still issues.A new doping mechanism for spiro-OMeTAD by disulfiram(TETD)is revealed in this work.Owing to its disulfide bond,TETD can be activated easily to produce reactive sulfur for the rapid oxidation of spiro-OMeTAD in the absence of oxygen with formation of[spiro-OMeTAD•]+[SC(S)N(C_(2)H_(5))_(2)]^(-).Thus,in this situation,the Li+ion has the opportunity to coordinate tBP and fix each other in HTM film.DFT calculations suggest that the resulting favorable energy(with a△E of−1.29 eV)must come from the mutual interactions among Li^(+),TFSI^(−),and tBP,which is different from the well-known doping process that tBP would not participate in the doping reaction.As a result,the introduction of a new radical into the HTM greatly reduce device performance fluctuations due to the environmental dependence and inhibit tBP volatilizing for enhanced long-term stability.展开更多
Nickel oxide(NiO_(x))is widely used as a hole transport material in inverted perovskite solar cells.However,its practical application is limited by its low intrinsic conductivity and insufficient hole extraction abili...Nickel oxide(NiO_(x))is widely used as a hole transport material in inverted perovskite solar cells.However,its practical application is limited by its low intrinsic conductivity and insufficient hole extraction ability,which leads to significant interfacial defect formation that reduces device efficiency and stability.To overcome these issues,small organic molecules(2,6-NOT and 1,5-NOT)have been developed and introduced to modify NiO_(x).The two molecules are isomers that share the same structure but differ in the substitution positions of the functional groups.The experimental results show that,compared with 2,6-NOT,1,5-NOT,featuring extended conjugation,more effectively enhances the hole extraction/transport capabilities and conductivity of NiO_(x).The NiO_(x)/1,5-NOT-based device achieves a remarkable power conversion efficiency of 24.20%,along with excellent longterm stability,surpassing those of the NiO_(x) control device(18.12%)and the 2,6-NOT-based device(21.87%).These findings demonstrate that modifying NiO_(x) with small organic molecules can significantly improve the charge transport performance and that increasing the molecular planarity is particularly beneficial for enhancing hole transport and reducing the number of defects,thereby increasing both the efficiency and stability.These results provide a new strategy for NiO_(x) modification via small organic molecules.展开更多
Inorganic Cu_(2)ZnSnS_(4)(CZTS)has garnered significant attention in the field of solar cells owing to its high hole mobility,suitable optical bandgap,cost-effective and earth-abundant elemental constituents.In partic...Inorganic Cu_(2)ZnSnS_(4)(CZTS)has garnered significant attention in the field of solar cells owing to its high hole mobility,suitable optical bandgap,cost-effective and earth-abundant elemental constituents.In particular,the deeper highest occupied molecular orbital(HOMO)of CZTS makes it an alternative for the traditional organic hole transport layer(HTL)material poly(3,4-ethyllenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS),which can suppress acidic interface and hygroscopic problem in perovskite lightemitting diodes(PeLEDs).Herein,we demonstrate CZTS as a novel inorganic HTL for green FAPbBr_(3)PeLEDs,achieving a peak external quantum efficiency(EQE)of 7.59%and a maximum luminance of 27000 cd m^(−2)(emitting at 529 nm).The fluorescence properties of the perovskite films and interfacial behaviors of CZTS/FAPbBr_(3)were investigated through surface state regulation of CZTS HTL.High hole mobility(0–30 cm^(2)V^(−1)s^(−1))of CZTS HTL and low hole injection barrier(∼0.13 eV)between CZTS and perovskite endow the CZTS-based PeLEDs with enhanced hole transport capability and suppressed interfacial carrier accumulation.In addition,an attractive cost-effectiveness advantage of aboutS0.24 per g synthesizing CZTS makes it a promising competitor to mainstream organic HTL materials such as PEDOT:PSS(∼S1.3 per g).An in-depth understanding of this novel CZTS HTL makes an essential step forward for the commercialization of PeLEDs.展开更多
The acidic, corrosive effect of sodium polystyrene sulfonate(PSS) in poly 3,4-ethylenedioxythiophene:sodium polystyrene sulfonate(PEDOT:PSS) limits the stability of inverted perovskite solar cells(PSCs) based on the I...The acidic, corrosive effect of sodium polystyrene sulfonate(PSS) in poly 3,4-ethylenedioxythiophene:sodium polystyrene sulfonate(PEDOT:PSS) limits the stability of inverted perovskite solar cells(PSCs) based on the ITO/PEDOT:PSS/perovskite/PCBM/BCP/Ag structure. In this work, a poly 3,4-ethylenedioxythiophene(PEDOT) hole transport layer(HTL) with high hole mobility and good catalytic performance was prepared by electrochemical cyclic voltammetry(CV) method for inverted PSCs. By controlling the CV cycles(from 1 to 5 cycles) and EDOT monomer solution concentration(from0.5 to 2.0 mmol·L^(-1)) of electrochemical deposition, the thickness, morphology, optical and electrochemical properties of PEDOT could be accurately adjusted. The optimal photovoltaic performance with current density(J_(sc)) of 22.19 mA·cm^(-2), open circuit voltage(V_(oc)) of 0.94 V, fill factor(FF) of 0.65 and photoelectric conversion efficiency of 13.56% was obtained when deposition of PEDOT with 1 CV cycle and EDOT concentration of 0.5 mmol·L^(-1). At this point, the perovskite showed good crystallization,optimal optical, charge transport and recombination performance, resulting in better V_(oc)and photoelectric conversion efficiency(PCE) compared to the devices with higher CV cycle numbers and 3,4-ethylenedioxythiophene(EDOT) concentration. For comparison with spin-coated PEDOT:PSS, the device with electrodeposited PEDOT showed improved J_(sc)and comparable V_(oc), which may result from its better charge transport and catalytic ability.The device with spin-coated PEDOT:PSS showed photoelectric conversion efficiency of 12.25%, which was lower than that based on electrodeposited PEDOT(13.56%) with1 CV cycles and 0.5 mmol·L^(-1) EDOT concentration. And the device with electrodeposited PEDOT as HTLs showed more excellent air stability. In ambient air((32 ± 5) ℃ and RH: 70% ± 20%), it still maintained more than 80%of the initial photoelectric conversion efficiency after1000 h. In comparison, the photoelectric conversion efficiency of the device with PEDOT:PSS decreased to 20% of the initial value after storage for 500 h. From this study, a facial and low-cost way to prepare PEDOT HTL with high performances that better than the traditional PEDOT:PSS has been explored, which is expected to eliminate the acidic, corrosive effect of PSS in PEDOT:PSS.展开更多
Ge and Si p-channel metal-oxide-semiconductor field-effect-transistors （p-MOSFETs） with hafnium silicon oxynitride （HfSiON） gate dielectric and tantalum nitride （TAN） metal gate are fabricated. Self-isolated rin...Ge and Si p-channel metal-oxide-semiconductor field-effect-transistors （p-MOSFETs） with hafnium silicon oxynitride （HfSiON） gate dielectric and tantalum nitride （TAN） metal gate are fabricated. Self-isolated ring-type transistor structures with two masks are employed. W/TaN metal stacks are used as gate electrode and shadow masks of source/drain implantation separately. Capacitance-voltage curve hysteresis of Ge metal-oxide-semiconductor （MOS） capacitors may be caused by charge trapping centres in GeOx （1 〈 x 〈 2）. Effective hole mobilities of Ge and Si transistors are extracted by using a channel conductance method. The peak hole mobilities of Si and Ge transistors are 33.4 cm2/（V.s） and 81.0 cm2/（V.s）, respectively. Ge transistor has a hole mobility 2.4 times higher than that of Si control sample.展开更多
Tin-based perovskites have emerged as promising semiconductor materials for high-performance field-effect transistors(FETs).However,poor film quality of tin-based perovskites seriously impedes carrier transport and de...Tin-based perovskites have emerged as promising semiconductor materials for high-performance field-effect transistors(FETs).However,poor film quality of tin-based perovskites seriously impedes carrier transport and degrades operational stability of the FETs.In this study,we propose a bifunctional additive strategy employing 4-fluorophenethylamine acetate(FPEAAc)to regulate the crystallization of Sn-based perovskites,resulting in preferentially oriented,fully covered and large-grained perovskite films.The FPEA+cations induced the templating growth of perovskite octahedron,while Ac^(-)anions retard the crystallization growth to promote uniform films.To further enhance grain size while maintaining pinhole-free morphology,propylammonium acetate(PAAc)additive is introduced as an auxiliary additive to further delay crystal growth.The optimized FETs demonstrate a high hole mobility of~40 cm^(2)V^(-1)s^(-1)along with excellent operational stability.This work establishes a co-additive strategy that precisely regulates tin-based perovskite crystallization through templated growth coupled with retarded crystallization,offering novel insights into regulating the film growth of Sn-based perovskites,and thereby advancing the development of high-performance perovskite FETs.展开更多
Lithium bis(trifluoromethanesulfonyl)imide is commonly employed as a dopant to improve the hole mobility of hole transport layers.However,undesired Li^(+)migration impedes the development of highly efficient and stabl...Lithium bis(trifluoromethanesulfonyl)imide is commonly employed as a dopant to improve the hole mobility of hole transport layers.However,undesired Li^(+)migration impedes the development of highly efficient and stable perovskite solar cells because the voids left by Li^(+)migration will accelerate the penetration of oxygen and moisture.展开更多
Biaxial strain technology is a promising way to improve the mobility of both electrons and holes, while （100） channel direction appears as to be an effective booster of hole mobility in particular. In this work, the...Biaxial strain technology is a promising way to improve the mobility of both electrons and holes, while （100） channel direction appears as to be an effective booster of hole mobility in particular. In this work, the impact of biaxial strain together with （100） channel orientation on hole mobility is explored. The biaxial strain was incorporated by the growth of a relaxed SiGe buffer layer,serving as the template for depositing a Si layer in a state of biaxial tensile strain. The channel orientation was implemented with a 45^o rotated design in the device layout,which changed the channel direction from （110） to （100） on Si （001） surface. The maximum hole mobility is enhanced by 30% due to the change of channel direction from （110） to （100） on the same strained Si （s-Si） p-MOSFETs,in addition to the mobility enhancement of 130% when comparing s-Si pMOS to bulk Si pMOS both along （110） channels. Discussion and analysis are presented about the origin of the mobility enhancement by channel orientation along with biaxial strain in this work.展开更多
The electroluminescent characteristics of blue organic light-emitting diodes （BOLEDs） fabricated with doped charge carrier transport layers are analyzed. The fluorescent blue dopant BCzVBi is doped in an emissive la...The electroluminescent characteristics of blue organic light-emitting diodes （BOLEDs） fabricated with doped charge carrier transport layers are analyzed. The fluorescent blue dopant BCzVBi is doped in an emissive layer, hole transport layer （HTL） and electron transport layer （ETL）, respectively, to optimize the probability of ex- citon generation in the BOLEDs. The luminance and luminous efficiency of BOLEDs made with BCzVBi-doped HTL and ETL increase by 22% and 17% from 11,683 cd/m2 at 8.5 V and 6.08 cd/A at 4.0 V to 14,264 cd/m2 at 8.5 V and 7.13 cd/A at 4.0 V while CIE coordinates of （0.15, 0.15） of both types of BOLEDs remained unchanged. The electron mobility of BCzVBi is estimated to be 1.02 × 10-5 cm2/Vs by TOF.展开更多
基金supported by the financial supports from National Natural Science Foundation of China(Grant No.61904110)Young Teachers’Startup Fund for Scientific Research of Shenzhen University(Grant No.860-000002110426)+2 种基金the funding support from the National Natural Science Foundation of China(52122002)the Start-Up Grant(Project No.9610495)from City University of Hong KongECS scheme(City U 21201821)from the Research Grant Council of Hong Kong。
文摘The lack of stable p-type van der Waals(vdW)semiconductors with high hole mobility severely impedes the step of low-dimensional materials entering the industrial circle.Although p-type black phosphorus(bP)and tellurium(Te)have shown promising hole mobilities,the instability under ambient conditions of bP and relatively low hole mobility of Te remain as daunting issues.Here we report the growth of high-quality Te nanobelts on atomically flat hexagonal boron nitride(h-BN)for high-performance p-type field-effect transistors(FETs).Importantly,the Te-based FET exhibits an ultrahigh hole mobility up to 1370 cm^(2) V^(−1) s^(−1) at room temperature,that may lay the foundation for the future high-performance p-type 2D FET and metal-oxide-semiconductor(p-MOS)inverter.The vdW h-BN dielectric substrate not only provides an ultra-flat surface without dangling bonds for growth of high-quality Te nanobelts,but also reduces the scattering centers at the interface between the channel material and the dielectric layer,thus resulting in the ultrahigh hole mobility.
基金This work was supported in part by the Natural Science Foundation of China under Grant 62174019in part by the Guangdong Basic and Applied Basic Research Foundation China under Grant 2021B1515140039in part by the Zhuhai Industry-University Research Cooperation Project under Grant ZH22017001210041PWC.
文摘In this work,the GaN p-MISFET with LPCVD-SiN_(x) is studied as a gate dielectric to improve device performance.By changing the Si/N stoichiometry of SiN_(x),it is found that the channel hole mobility can be effectively enhanced with Si-rich SiN_(x) gate dielectric,which leads to a respectably improved drive current of GaN p-FET.The record high channel mobility of 19.4 cm2/(V∙s)was achieved in the device featuring an Enhancement-mode channel.Benefiting from the significantly improved channel mobility,the fabricated E-mode GaN p-MISFET is capable of delivering a decent-high current of 1.6 mA/mm,while simultaneously featuring a negative threshold-voltage(VTH)of–2.3 V(defining at a stringent criteria of 10μA/mm).The device also exhibits a well pinch-off at 0 V with low leakage current of 1 nA/mm.This suggests that a decent E-mode operation of the fabricated p-FET is obtained.In addition,the VTH shows excellent stability,while the threshold-voltage hysteresisΔVTH is as small as 0.1 V for a gate voltage swing up to–10 V,which is among the best results reported in the literature.The results indicate that optimizing the Si/N stoichiometry of LPCVD-SiN_(x) is a promising approach to improve the device performance of GaN p-MISFET.
基金This work is supported by the National Key R&D Program of China(No.2021YFA1202200)the CAS Project for Young Scientists in Basic Research(No.YSBR-030)+1 种基金the National Natural Science Foundation Program of China(No.12174383)H L Wang also acknowledges the support from the Youth Innovation Promotion Association,Chinese Academy of Sciences(No.2021110).
文摘(Ga,Fe)Sb is a promising magnetic semiconductor(MS)for spintronic applications because its Curie temperature(T_(C))is above 300 K when the Fe concentration is higher than 20%.However,the anisotropy constant Ku of(Ga,Fe)Sb is below 7.6×10^(3)erg/cm^(3)when Fe concentration is lower than 30%,which is one order of magnitude lower than that of(Ga,Mn)As.To address this issue,we grew Ga_(1-x-y)Fe_(x)Ni_(y)Sb films with almost the same x(≈24%)and different y to characterize their magnetic and electrical transport properties.We found that the magnetic anisotropy of Ga_(0.76-y)Fe_(0.24)Ni_(y)Sb can be enhanced by increasing y,in which Ku is negligible at y=1.7%but increases to 3.8×10^(5)erg/cm^(3)at y=6.1%(T_(C)=354 K).In addition,the hole mobility(μ)of Ga_(1-x-y)Fe_(x)Ni_(y)Sb reaches 31.3 cm^(2)/(V∙s)at x=23.7%,y=1.7%(T_(C)=319 K),which is much higher than the mobility of Ga_(1-x)Fe_(x)Sb at x=25.2%(μ=6.2 cm^(2)/(V∙s)).Our results provide useful information for enhancing the magnetic anisotropy and hole mobility of(Ga,Fe)Sb by using Ni co-doping.
基金supported by the National Natural Science Foundation of China(Grant Nos.51071038and60576007)Program for New Century Excellent Talents in University(NCET-09-0265)the Sichuan Province Science Foundation for Youths(No.2010JQ0002)
文摘The structural property of GaSb epilayers grown on semi-insulator GaAs （001） substrate by metalorganic chemical vapor deposition （MOCVD） using Triethylgallium （TEGa） and trimethylantimony （TMSb）, was investigated by variation of the Sb：Ga （V/Ill） ratio. An optimum V/Ill ratio of 1.4 was determined in our growth conditions. Using transmission electron microscopy （TEM）, we found that there was an interracial misfit dislocations （IMF） growth mode in our experiment, in which the large misfit strain between epilayer and substrate is relaxed by periodic 90 deg. IMF array at the hetero-epitaxial interface. The rms roughness of a 300 nm-thick GaSb layer is only 2.7 nm in a 10μm×10μm scan from atomic force microscopy （AFM） result. The best hole density and mobility of 300 nm GaSb epilayer are 5.27xi06 cm-3（1.20×106） and 553 cm2-V-l.s-1 （2340） at RT （77 K） from Hall measurement, respectively. These results indicate that the IMF growth mode can be used in MOCVD epitaxial technology similar to molecular beam epitaxy （MBE） technology to produce the thinner GaSb layer with low density of dislocations and other defects on GaAs substrate for the application of devices.
基金supported by the National Key Research and Development Program of China(2016YFA0302300,016YFA0200400)the National Science and Technology Major Project of China(2016ZX02301001)+1 种基金the National Natural Science Foundation of China(61306105)the Tsinghua University Initiative Scientific Research Program
文摘Molybdenum ditelluride （MoTe2） has been demonstrated great potential in electronic and optoelectronic applications. However, the reported effective hole mobility remains far below its theoretical value. Herein, taking advantage of high-κ screening effect, we have fabricated back-gated MoTe2 transistors on an Al2O3 high-κ dielectric and systematically investigated the electronic and optoelectronic proper- ties. A high current on/off ratio exceeding 106 is achieved in the Al2O3-based MoTe2 transistors, and the hole mobility is demonstrated to be 150 cm2 V^-1 s^-1, compared to 0.2-20 cm^2 V^-1 s^-1 ever obtained from back-gated MoTe2 transistors in the literatures. Moreover, a considerable hole concentration of 1.2 × 10^13 cm 2 is attained in our Al2O3-based MoTe2 transistors owing to the strong gate control capa- bility, leading to a high on-state hole current of 6.1 μA μm^-1. After optimization, our Al2O3-based MoTe2 phototransistor exhibits outstanding photodetective performance, with a high responsivity of 543 AW^-1 and a high photogain of 1,662 at 405 nm light illumination, which are boosted around 419 times compared to the referential SiO2-based control devices. The mechanisms of photoconductivity in the Al2O3-based MoTe2 phototransistors have been analyzed in detail, and the photogating effect is considered to play an important role. This work may provide useful insight to improve carrier mobility in two-dimensional layered semiconductors and open opportunities to facilitate the development of high-performance photodetectors in the future.
基金supported by the National Key Research and Development Program of China(2017YFB0405702)the National Natural Science Foundation of China(52172272)。
文摘In this work,silicon-germanium(SiGe)thin films are epitaxially grown on Ge substrates by ultra-high vacuum chemical vapor deposition and then doped with Mn element by ion-implantation and subsequent rapid thermal annealing(RTA).The characterizations show that the epitaxial SiGe thin films are single-crystalline with uniform tensile strain and then become polycrystalline after the ion implantation and following RTA.The magnetization measurements indicate that the annealed thin films exhibit Mn concentration-dependent ferromagnetism up to 309 K and the X-ray magnetic circular dichroism characterizations reveal the spin and orbital magnetic moments from the substitutional Mn element.To minimize the influence of anomalous Hall effect,magneto-transport measurements at a high magnetic field up to 31 T at 300 K are performed to obtain the hole mobility,which reaches a record-high value of~1230 cm^(2)V^(-1)s^(-1),owing to the crystalline quality and tensile strain-induced energy band modulation of the samples.The first demonstration of Mn-doped SiGe thin films with roomtemperature ferromagnetism and high carrier mobility may pave the way for practical semiconductor spintronic applications.
基金supported by the National Natural Science Foundation of China(Grant No.51272150)the Postdoctoral Science Foundation of Shaanxi Province of China
文摘Utilizing a six-band k.p valence band calculations that considered a strained perturbation Hamiltonian, uniaxial stress-induced valence band structure parameters for Ge such as band edge energy shift, split, and effective mass were quantitatively evaluated. Based on these valence band parameters, the dependence of hole mobility on uniaxial stress(direction, type, and magnitude) and hole transport direction was theoretical studied. The results show that the hole mobility had a strong dependence on the transport direction and uniaxial stress. The hole mobility enhancement can be found for all transport directions and uniaxial stess configurations, and the hole transport along the [110] direction under the uniaxial [110] compressive stress had the highest mobility compared to other transport directions and stress configurations.
基金Project supported by the National Natural Science Foundation of China(Nos.61274112,61176100,61404055)
文摘A physical model of hole mobility for germanium-on-insulator p MOSFETs is built by analyzing all kinds of scattering mechanisms, and a good agreement of the simulated results with the experimental data is achieved, confirming the validity of this model. The scattering mechanisms involved in this model include acoustic phonon scattering, ionized impurity scattering, surface roughness scattering, coulomb scattering and the scattering caused by Ge film thickness fluctuation. The simulated results show that the coulomb scattering from the interface charges is responsible for the hole mobility degradation in the low-field regime and the surface roughness scattering limits the hole mobility in the high-field regime. In addition, the effects of some factors, e.g. temperature, doping concentration of the channel and the thickness of Ge film, on degradation of the mobility are also discussed using the model, thus obtaining a reasonable range of the relevant parameters.
基金supported by the National Natural Science Foundation of China(Nos.60636010,60820106001)
文摘Hole mobility changes under uniaxial and combinational stress in different directions are characterized and analyzed by applying additive mechanical uniaxial stress to bulk Si and SiGe-virtual-substrate-induced strained- Si（s-Si）p-MOSFETs（metal-oxide-semiconductor field-effect transistors）along 110 and 100 channel directions. In bulk Si,a mobility enhancement peak is found under uniaxial compressive strain in the low vertical field.The combination of 100 direction uniaxial tensile strain and substrate-induced biaxial tensile strain provides a higher mobility relative to the 110 direction,opposite to the situation in bulk Si.But the combinational strain experiences a gain loss at high field,which means that uniaxial compressive strain may still be a better choice.The mobility enhancement of SiGe-induced strained p-MOSFETs along the 110 direction under additive uniaxial tension is explained by the competition between biaxial and shear stress.
基金supported by the National Ministries and Commissions (Grant Nos. 51308040203, 9140A08060407DZ0103 and 6139801)
文摘The hole mobility of strained silicon along the <110> orientation on (001) Si1?xGex is obtained by solving collision term in the Boltzmann transport equation. The analytical model is proposed that considers the effect of strain-induced splitting at valence band valleys in silicon, doping dependence and three scattering mechanisms, i.e., ionized impurity scattering, acoustic phonon scattering and non-polar optical phonon scattering. The hole occupancy at top band indicates a non-monotonic variation under biaxial tensile strain at low temperature (77 K). What's more, a non-monotonic variation of hole mobility at room temperature (300 K) is presented. Compared with the room temperature hole mobility, the low temperature hole mobility is affected greatly by ionized impurity scattering at lower impurity concentration. At the same time, the room temperature hole mobility is lower than that of electron with the same germanium content and doping concentration. If the parameters are correctly chosen, the model can also be used to calculate the hole mobility of other crystal faces with arbitrary orientation. So, it lays a useful foundation for strained silicon devices and circuits.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11925407 and 61927901)the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(Grant No.ZDBS-LY-JSC019).
文摘First-principles approaches have recently been developed to replace the phenomenological modeling approaches with adjustable parameters for calculating carrier mobilities in semiconductors.However,in addition to the high computational cost,it is still a challenge to obtain accurate mobility for carriers with a complex band structure,e.g.,hole mobility in common semiconductors.Here,we present a computationally efficient approach using isotropic and parabolic bands to approximate the anisotropy valence bands for evaluating group velocities in the first-principles calculations.This treatment greatly reduces the computational cost in two ways:relieves the requirement of an extremely denseκmesh to obtain a smooth change in group velocity,and reduces the 5-dimensional integral to 3-dimensional integral.Taking Si and SiC as two examples,we find that this simplified approach reproduces the full first-principles calculation for mobility.If we use experimental effective masses to evaluate the group velocity,we can obtain hole mobility in excellent agreement with experimental data over a wide temperature range.These findings shed light on how to improve the first-principles calculations towards predictive carrier mobility in high accuracy.
基金supported by the National Natural Science Foundation of China(Nos.52001066,21805039,22375045,22373015 and 22271046)the Natural Science Foundation of Fujian Province(No.2023J01500)Young teacher training program of Fujian Normal University(No.SDPY2023013).
文摘Although lots of efforts have been devoted on new less hygroscopic dopants to address problems in hole transport materials(HTM),the long-time post-oxidation and the volatilization of 4-tert-butylpyridine(tBP)are still issues.A new doping mechanism for spiro-OMeTAD by disulfiram(TETD)is revealed in this work.Owing to its disulfide bond,TETD can be activated easily to produce reactive sulfur for the rapid oxidation of spiro-OMeTAD in the absence of oxygen with formation of[spiro-OMeTAD•]+[SC(S)N(C_(2)H_(5))_(2)]^(-).Thus,in this situation,the Li+ion has the opportunity to coordinate tBP and fix each other in HTM film.DFT calculations suggest that the resulting favorable energy(with a△E of−1.29 eV)must come from the mutual interactions among Li^(+),TFSI^(−),and tBP,which is different from the well-known doping process that tBP would not participate in the doping reaction.As a result,the introduction of a new radical into the HTM greatly reduce device performance fluctuations due to the environmental dependence and inhibit tBP volatilizing for enhanced long-term stability.
基金financially supported by the National Natural Science Foundation of China (22475178)Fundamental Research Funds for the Central Universities (SWU-XDJH202314)。
文摘Nickel oxide(NiO_(x))is widely used as a hole transport material in inverted perovskite solar cells.However,its practical application is limited by its low intrinsic conductivity and insufficient hole extraction ability,which leads to significant interfacial defect formation that reduces device efficiency and stability.To overcome these issues,small organic molecules(2,6-NOT and 1,5-NOT)have been developed and introduced to modify NiO_(x).The two molecules are isomers that share the same structure but differ in the substitution positions of the functional groups.The experimental results show that,compared with 2,6-NOT,1,5-NOT,featuring extended conjugation,more effectively enhances the hole extraction/transport capabilities and conductivity of NiO_(x).The NiO_(x)/1,5-NOT-based device achieves a remarkable power conversion efficiency of 24.20%,along with excellent longterm stability,surpassing those of the NiO_(x) control device(18.12%)and the 2,6-NOT-based device(21.87%).These findings demonstrate that modifying NiO_(x) with small organic molecules can significantly improve the charge transport performance and that increasing the molecular planarity is particularly beneficial for enhancing hole transport and reducing the number of defects,thereby increasing both the efficiency and stability.These results provide a new strategy for NiO_(x) modification via small organic molecules.
基金supported by the National Natural Science Foundation of China(No.52202188 and 11704050).
文摘Inorganic Cu_(2)ZnSnS_(4)(CZTS)has garnered significant attention in the field of solar cells owing to its high hole mobility,suitable optical bandgap,cost-effective and earth-abundant elemental constituents.In particular,the deeper highest occupied molecular orbital(HOMO)of CZTS makes it an alternative for the traditional organic hole transport layer(HTL)material poly(3,4-ethyllenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS),which can suppress acidic interface and hygroscopic problem in perovskite lightemitting diodes(PeLEDs).Herein,we demonstrate CZTS as a novel inorganic HTL for green FAPbBr_(3)PeLEDs,achieving a peak external quantum efficiency(EQE)of 7.59%and a maximum luminance of 27000 cd m^(−2)(emitting at 529 nm).The fluorescence properties of the perovskite films and interfacial behaviors of CZTS/FAPbBr_(3)were investigated through surface state regulation of CZTS HTL.High hole mobility(0–30 cm^(2)V^(−1)s^(−1))of CZTS HTL and low hole injection barrier(∼0.13 eV)between CZTS and perovskite endow the CZTS-based PeLEDs with enhanced hole transport capability and suppressed interfacial carrier accumulation.In addition,an attractive cost-effectiveness advantage of aboutS0.24 per g synthesizing CZTS makes it a promising competitor to mainstream organic HTL materials such as PEDOT:PSS(∼S1.3 per g).An in-depth understanding of this novel CZTS HTL makes an essential step forward for the commercialization of PeLEDs.
基金financially supported by the National Natural Science Foundation of China(No.61774169)Qingyuan Innovation and Entrepreneurship Research Team Project(No.2018001)。
文摘The acidic, corrosive effect of sodium polystyrene sulfonate(PSS) in poly 3,4-ethylenedioxythiophene:sodium polystyrene sulfonate(PEDOT:PSS) limits the stability of inverted perovskite solar cells(PSCs) based on the ITO/PEDOT:PSS/perovskite/PCBM/BCP/Ag structure. In this work, a poly 3,4-ethylenedioxythiophene(PEDOT) hole transport layer(HTL) with high hole mobility and good catalytic performance was prepared by electrochemical cyclic voltammetry(CV) method for inverted PSCs. By controlling the CV cycles(from 1 to 5 cycles) and EDOT monomer solution concentration(from0.5 to 2.0 mmol·L^(-1)) of electrochemical deposition, the thickness, morphology, optical and electrochemical properties of PEDOT could be accurately adjusted. The optimal photovoltaic performance with current density(J_(sc)) of 22.19 mA·cm^(-2), open circuit voltage(V_(oc)) of 0.94 V, fill factor(FF) of 0.65 and photoelectric conversion efficiency of 13.56% was obtained when deposition of PEDOT with 1 CV cycle and EDOT concentration of 0.5 mmol·L^(-1). At this point, the perovskite showed good crystallization,optimal optical, charge transport and recombination performance, resulting in better V_(oc)and photoelectric conversion efficiency(PCE) compared to the devices with higher CV cycle numbers and 3,4-ethylenedioxythiophene(EDOT) concentration. For comparison with spin-coated PEDOT:PSS, the device with electrodeposited PEDOT showed improved J_(sc)and comparable V_(oc), which may result from its better charge transport and catalytic ability.The device with spin-coated PEDOT:PSS showed photoelectric conversion efficiency of 12.25%, which was lower than that based on electrodeposited PEDOT(13.56%) with1 CV cycles and 0.5 mmol·L^(-1) EDOT concentration. And the device with electrodeposited PEDOT as HTLs showed more excellent air stability. In ambient air((32 ± 5) ℃ and RH: 70% ± 20%), it still maintained more than 80%of the initial photoelectric conversion efficiency after1000 h. In comparison, the photoelectric conversion efficiency of the device with PEDOT:PSS decreased to 20% of the initial value after storage for 500 h. From this study, a facial and low-cost way to prepare PEDOT HTL with high performances that better than the traditional PEDOT:PSS has been explored, which is expected to eliminate the acidic, corrosive effect of PSS in PEDOT:PSS.
基金Project supported by the National Basic Research Program of China (Grant No. 2006CB302704)
文摘Ge and Si p-channel metal-oxide-semiconductor field-effect-transistors （p-MOSFETs） with hafnium silicon oxynitride （HfSiON） gate dielectric and tantalum nitride （TAN） metal gate are fabricated. Self-isolated ring-type transistor structures with two masks are employed. W/TaN metal stacks are used as gate electrode and shadow masks of source/drain implantation separately. Capacitance-voltage curve hysteresis of Ge metal-oxide-semiconductor （MOS） capacitors may be caused by charge trapping centres in GeOx （1 〈 x 〈 2）. Effective hole mobilities of Ge and Si transistors are extracted by using a channel conductance method. The peak hole mobilities of Si and Ge transistors are 33.4 cm2/（V.s） and 81.0 cm2/（V.s）, respectively. Ge transistor has a hole mobility 2.4 times higher than that of Si control sample.
基金supported by the National Natural Science Foundation of China(62321166653 and 62125402)the Natural Science Foundation of Jilin Province(20230101105JC)。
文摘Tin-based perovskites have emerged as promising semiconductor materials for high-performance field-effect transistors(FETs).However,poor film quality of tin-based perovskites seriously impedes carrier transport and degrades operational stability of the FETs.In this study,we propose a bifunctional additive strategy employing 4-fluorophenethylamine acetate(FPEAAc)to regulate the crystallization of Sn-based perovskites,resulting in preferentially oriented,fully covered and large-grained perovskite films.The FPEA+cations induced the templating growth of perovskite octahedron,while Ac^(-)anions retard the crystallization growth to promote uniform films.To further enhance grain size while maintaining pinhole-free morphology,propylammonium acetate(PAAc)additive is introduced as an auxiliary additive to further delay crystal growth.The optimized FETs demonstrate a high hole mobility of~40 cm^(2)V^(-1)s^(-1)along with excellent operational stability.This work establishes a co-additive strategy that precisely regulates tin-based perovskite crystallization through templated growth coupled with retarded crystallization,offering novel insights into regulating the film growth of Sn-based perovskites,and thereby advancing the development of high-performance perovskite FETs.
基金supported by the National Natural Science Foundation of China(U21A20172,61804091,and U21A6004)Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(2020L0002)+2 种基金the Natural Science Foundation of Shanxi Province under Grant(201901D211127)the Program of the State Key Laboratory of Quantum Optics and Quantum Optics Devices(No.KF201910)the Scientific Research Start-up Funds of Shanxi University,Hundred Talents Plan of Shanxi Province,Quanzhou“Tong Jiang Scholar”Program,and Fujian Natural Science Funds for Distinguished Young Scholars(2020J06046).
文摘Lithium bis(trifluoromethanesulfonyl)imide is commonly employed as a dopant to improve the hole mobility of hole transport layers.However,undesired Li^(+)migration impedes the development of highly efficient and stable perovskite solar cells because the voids left by Li^(+)migration will accelerate the penetration of oxygen and moisture.
文摘Biaxial strain technology is a promising way to improve the mobility of both electrons and holes, while （100） channel direction appears as to be an effective booster of hole mobility in particular. In this work, the impact of biaxial strain together with （100） channel orientation on hole mobility is explored. The biaxial strain was incorporated by the growth of a relaxed SiGe buffer layer,serving as the template for depositing a Si layer in a state of biaxial tensile strain. The channel orientation was implemented with a 45^o rotated design in the device layout,which changed the channel direction from （110） to （100） on Si （001） surface. The maximum hole mobility is enhanced by 30% due to the change of channel direction from （110） to （100） on the same strained Si （s-Si） p-MOSFETs,in addition to the mobility enhancement of 130% when comparing s-Si pMOS to bulk Si pMOS both along （110） channels. Discussion and analysis are presented about the origin of the mobility enhancement by channel orientation along with biaxial strain in this work.
基金supported by the Ministry of Education,Science,and Technology (MEST)
文摘The electroluminescent characteristics of blue organic light-emitting diodes （BOLEDs） fabricated with doped charge carrier transport layers are analyzed. The fluorescent blue dopant BCzVBi is doped in an emissive layer, hole transport layer （HTL） and electron transport layer （ETL）, respectively, to optimize the probability of ex- citon generation in the BOLEDs. The luminance and luminous efficiency of BOLEDs made with BCzVBi-doped HTL and ETL increase by 22% and 17% from 11,683 cd/m2 at 8.5 V and 6.08 cd/A at 4.0 V to 14,264 cd/m2 at 8.5 V and 7.13 cd/A at 4.0 V while CIE coordinates of （0.15, 0.15） of both types of BOLEDs remained unchanged. The electron mobility of BCzVBi is estimated to be 1.02 × 10-5 cm2/Vs by TOF.
